A BIOLOGICAL EXAMINATION OF DISTILLED 



WATER. 



E. P. LYON. 



The accuracy of results obtained in many of the present lines 

 of physiological research depends so entirely on the purity of the 

 chemicals used, including water, that I may be pardoned for pub- 

 lishing an account of work which otherwise would have little sig- 

 nificance, the toxicity of metal-distilled water having been re- 

 peatedly shown. The results obtained are, however, applicable 

 in a practical way at Woods Hole, where it is difficult to get 

 good distilled water. 



Two years ago I arranged an automatic still in which the 

 water was boiled in a block tin vessel but the dry steam received 

 and condensed in glass. It was thought that if the water did not 

 touch metal after condensation, contamination by ions would be 

 avoided. The distillate proved, however, to be decidedly toxic. 

 I could not believe that dry steam carried with it an appreciable 

 quantity of metal and, therefore, decided to find out where the 

 trouble lay. 



In these experiments, sea-water was condensed to a known 

 fraction of its volume and then measured portions brought back 

 to the original volume by adding the distilled waters to be tested. 

 Tap-water was also used for comparison ; sometimes, without 

 treatment ; sometimes, sterilized without boiling ; in some experi- 

 ments a portion was boiled away and the remaining portion used. 



To the artificial sea-waters prepared as above equal amounts 

 of fertilized Arbacia eggs were added and the development ob- 

 served. The percentage of plutei developed in the different so- 

 lutions as compared with natural sea-water was usually taken as 

 a measure of purity. In other cases, the percentage of blastula; 

 was the standard ; or the percentage of segmentation in a given 

 time ; or the length of time that any larvee remained alive. The 

 records of some typical experiments follow : 



Experiment 6. --250 c.c. sea-water were concentrated to 75 

 c.c. To each 15 c.c. of this solution 35 c.c. of the waters named 



198 



